The present invention relates to a permanent magnet rotor or an asynchronous squirrel-cage rotor with a hollow cylindrical magnet device which has permanent magnets and which is releasably mountable again on a shaft.
Sleeveless permanent magnet rotors are normally mounted upon a spindle shaft through friction fit by means of thermal joining for play-free torque transmission. As a result of the friction fitting or force locking joint, a detachment becomes impossible or is possible only by an accompanied impairment of the armature. Detachable units require sleeve configurations in which the laminated armature core, including the permanent magnets or the squirrel-cage, are mounted onto a sleeve. Such a rotor is illustrated in FIG. 1. The laminated armature core 1 including the permanent magnets is arranged radially above the armature sleeve 2. The armature sleeve 2 is constructed as oil-press joint in order to be able to detach the rotor from the spindle shaft again through use of oil pressure. The sleeve 2 includes hereby oil inlet bores 3. In such an armature sleeve 2, the axle hole diameter of the laminated armature core is reduced to the inner diameter D of the armature sleeve 2. Thus, the static and dynamic stiffness of the motor spindle decreases as a result of the limitation of the shaft outer diameter and limits the maximally attainable bar passage. In addition, the torque transmission requires a minimum joint pressure because a certain minimum torque should be transmitted across the force-locking connection between armature sleeve 2 and spindle shaft. The transmittable torque is defined by the joint force multiplied by the contact pressure surface. As a consequence, the joint pressure can be reduced at greater contact pressure surface, i.e. at greater axle hole diameter, and the maximum joint pressure resulting as a consequence of manufacturing tolerances can be reduced through adjustable clamping.
The compression or the joint pressure may cause a deformation of the shaft or of the work spindle, which deformation requires extensive refinishing work. For manufacturing reasons, the actual joint pressure is obtained from the minimum joint pressure and the pressure encountered in addition by the finishing tolerance of the shaft and the finishing tolerance of the sleeve. As a result, the joint pressure is subjected to very wide fluctuations which together with a resultant shaft deformation can be coped with only with great difficulty.
In order to be able to better manage the deformations of the shaft and to reduce the manufacturing and assembly costs, a stepped compression is applied between armature sleeve 2 and shaft, as indicated in FIG. 1 by the shaping of the inside surface area of the armature sleeve 2. Both end zones have hereby a compression zone 4, 5, respectively, which must have the stringent dimensional tolerances for the compression. It is easy to recognize that such a rotor, detachable from the shaft, can be manufactured only at substantial manufacturing costs and that the sleeve limits the outer shaft diameter.